1. Field of the Invention
The present invention relates to a fingerprint scanning device and an electronic device with a fingerprint scanning function and, more particularly, to a fingerprint scanning device combining a highly-compatible data transmission/control interface and a unit of electronic device with a fingerprint scanning function.
2. Description of Related Art
A personal fingerprint is a unique bio-feature different from those of others. When used as a personal secret code, it is extremely secure. Because of the popularity of electronic device and the increase of their storage capacities, the protection for personal data stored therein becomes increasingly important. Using a fingerprint for unlocking electronic device or as a secret code can make management of personal data more efficient.
Electronic device such as a mobile phone, a computer host, and various kinds of computer peripherals can make use of a fingerprint scanning device to capture a user's fingerprint for identity confirmation. After the fingerprint image in the fingerprint scanning device is converted into digital fingerprint information, it is easy to transmit the digital fingerprint information to a controller in the electronic device to exploit fully the effect of fingerprint identification.
The fingerprint scanning device has an image sensing module. The image sensing module can be of a planar or linear shape for capturing an image. The image detection way of the image sensing module can be of capacitance type, temperature type, or electromagnetic type. In the disclosure of U.S. Pat. No. 6,088,585, “Portable telecommunication device including a fingerprint sensor and related methods” issued on Jul. 11, 2000, an array of electric field sensing electrodes is provided. In order to avoid electrostatic interference, an electrostatic protection device must be added to the telecommunication device, hence increasing the cost. Moreover, damage may easily arise due to the generation of static electricity during the production process. Besides, the finger touching the array of electric field sensing electrodes may cause damage. On the other hand, because the time for a finger to stay on the image sensing module is too long, a temperature type image sensing module cannot capture a clear fingerprint image.
In order to capture a planar fingerprint image, a linear type image sensing module needs to be able to sense the speed of the finger moving thereon to acquire segments of fingerprint image, which are further processed to form a complete fingerprint image.
A prior art image sensing module with a motion sensing function such as that disclosed in Taiwan Pat. No. TW544630, “Method and device of using a linear sensor to scan a fingerprint”, comprises a linear image device, a roller, a light source, a focusing device and a rotation sensor. A fingerprint moves on the roller. Light of the light source is transmitted to the roller and reflected by the fingerprint to the focusing device, and is focused by the focusing device onto the linear image device. The rotation sensor is used to detect the rotating speed of the roller to acquire the speed of the fingerprint.
In the above prior art image sensing module with a speed detection function, the roller and the rotation sensor are used to determine the speed of the fingerprint, hence resulting in a bulky and complex image sensing module, which is not suitable for installation in miniaturized electronic device.
Moreover, there must be no deviation of the location of the focusing device, so that light can be accurately transmitted to the linear image device. The allowable tolerance is small, thus requiring precision to be too high in the assembly process, hence reducing the product yield.
Besides, the brightness of the light of the light source transmitted to the roller is not uniform enough, thus complicating processing of the fingerprint captured by the prior art image sensing module.
Furthermore, if the number of light sources is increased and these light sources are alternatingly arranged below the roller, the problem of irregular light brightness still exists, and the cost and consumed power of the image sensing module also increase.